Composition for copying-pads.



UNITED, STATES PATENT onnion.

ltUYALL OSCAR EUGENE DAVIS, ()F ()IlIEI/ HILL, NORTH CAROLINA, ASSIGNUR 0F UXII- THIRD TO RISDEN 'l. ALLEN, (11 CHAPEL HILL, NORTH CAROLINA.

COMPOSITION FOR COPYING-PADS.

Specification of Letters Patent.

Patented Jan. 5, 1909.

Application and March 12. 196a Serial No. 420,139.

To all whom it may concern:

lle it known that l, ROYAL], Osmn l'lr- GENE DAVIS, a citizen of the United Stules, and a resident oi" (hapel Hill, in the county of Orange and State of North (m-oliua. have.

invented a new and Improved Composition for Copying-Hula, of which the following is a full, clear. and exact description.

My invention relates to compositions for copying pads, my more particular purpose being toproduro a composition tablet having certain desirable properties hereinafter described, and. used for the purpose of making repented copies of characters made by ink upon paper. As is well understood in this art, it is a common practice to prepare a pad incapable of absorbing it to such anextent that it becomes lost in the composition.

I find it very desirable in making and using tablets for-the purpose above indicated, to render the tablet capable of conforming to various conditions due to changes in the atmosphere, and particularly to the amount of j forms a solution, but at 100 1t is capable of mmsture' present. I accordingly make my tablet of such composition that, in case the atmosphere happens to be excessively dry or excessively damp, the tablet, because of' its com osition, under oes slight changes in con ition, so that tIie amount of moisture resent in the atmosphere is not allowed to mterfere with the pro or operation of the tablet or of the materia s of which it is comgosed. I take a metal-lined wooden tray and I my pre aration into it so as to bring the surface of t e composition flush with the upper level of the tray, and allow the material to remain in the tra thereafter. The ('oin position is made of t is following materials in the proportions by weight as stated: aluminum oxid, 78 parts, silica (in the form of sand), 92 parts, potassium carbonate, 1 part,

, calcium sulfate, 10 'paits, and glycerin, 64

ink to a large number 1 In preparing such tab purls. mixed together, a little water is poured in with them, and the whole kneaded like dough and placed in the metal-lined wooden tray so as to lill it completely as above described, the upper level of theeomposilion being smoothed oil for use as n copying surface. In order to use the tablet thus made, I place upon it, l'nee do uwardly, a sheet of paper from whirh the Written words or other intelligible characters are to be copied. Pressure is applied in the usual manner so that the ink from the mpcr is absorbed slightly by the upper sur are of the tablet. The pressure is continued for about a minute; the paper is then removed and replaced by a blank sheet of paper, to which pressure is ap died as before. The sheet last mentioned being removed, will show on its under face a fee-simile of the characters appearing upon the original sheet. A considerable number of coples can thus be made, the general action of the tablet after its formation, being substan- These ingredients are thoroughly tially similar to that of other tablets heretofore used.

As is'well known potassium carbonate varies in composition with regard to the water content, but the amount of water it can attract and hold varies with the chan es in the atmosphere. This is true because 1; e vapor pressure of potassium carbonate varies with the temperature. Ordinarily it contains 3 molecules of water at a temperature of 32 with the power of attracting more water from the atmosphere until it holding only one molecule of Water, and at a somewhat higher temperature its vapor pressure is so great that it can hold no water. Hence the composition of the water content will vary materially for a small range of'tempcraturo. For this reason when the temperature rises and the composition tends to soften due to the greater fluidity of lycerin 'at the higher temperature, such lZGIlL ency is potassium carbonate 1 part, calcium sul-l l set forth.

fate 10 parts, and glycerin 64 parts.

2. A com osition for copying tablets consisting of alilminum oxid, silica, potassium carbonate, calcium sulfate, and lycerin in substantially the proportions set orth.

3. A composition for co ying tablets composed of substances ca ab 0 of absorbing and transn itting ink com )ined witl potassium carbonate in substantially the proportions 1':

,,In testimony whereof I have signed my name-tn this specification in the presence of two subscribing Witnesses.

KOYALL oscm EUGENE'DAVIS. Witnesses:

CLYDE' EUBANKS, RIsnnN T. ALLEN. 

